Promoting oxygen evolution of IrO2 in acid electrolyte by Mn

Simultaneously Improved Activity and Stability for Acidic Water Oxidation of IrRu Oxides by a Dual Role of Tungsten Doping

Acidic oxygen evolution reaction (OER) remains a significant challenge due to the low activity and/or poor stability of the catalysts, even with state-of-the-art catalysts such as IrO2 and RuO2. Herein, we propose a strategy to enhance both the catalytic activity and stability of IrRu oxides for acidic OER by doping non-noble metal W. The W-doped IrRu3Ox (W-IrRu3Ox) undergoes a process of W leaching and reconstruction during the OER, leading to a more uniform distribution of elements, while the electronegative nature of W influences the electronic structures of Ir and Ru in W-IrRu3Ox. The dual role of W in promoting the formation of active site Ir5+ and inhibiting the concentration of soluble Ru>4+ ions results in a synergistic enhancement of both the activity and stability of acidic OER. Remarkably, W-IrRu3Ox exhibits outstanding catalytic activity for the OER in 0.5 M H2SO4, with a high stability of more than 500 h. This work presents a novel and feasible strategy for the development of efficient and stable catalysts for acid OER, shedding light on the design of advanced electrocatalysts for energy conversion and storage applications.

Plasma-Assisted Atomic Layer Deposition of IrO2 for Neuroelectronics

In vitro and in vivo stimulation and recording of neuron action potential is currently achieved with microelectrode arrays, either in planar or 3D geometries, adopting different materials and strategies. IrO₂ is a conductive oxide known for its excellent biocompatibility, good adhesion on different substrates, and charge injection capabilities higher than noble metals. Atomic layer deposition (ALD) allows excellent conformal growth, which can be exploited on 3D nanoelectrode arrays. In this work, we disclose the growth of nanocrystalline rutile IrO₂ at T = 150 °C adopting a new plasma-assisted ALD (PA-ALD) process. The morphological, structural, physical, chemical, and electrochemical properties of the IrO₂ thin films are reported. To the best of our knowledge, the electrochemical characterization of the electrode/electrolyte interface in terms of charge injection capacity, charge storage capacity, and double-layer capacitance for IrO₂ grown by PA-ALD was not reported yet. IrO₂ grown on PtSi reveals a double-layer capacitance (C_dl) above 300 µF∙cm^-2, and a charge injection capacity of 0.22 ± 0.01 mC∙cm^-2 for an electrode of 1.0 cm², confirming IrO₂ grown by PA-ALD as an excellent material for neuroelectronic applications.

Selective Methane Oxidation by Heterogenized Iridium Catalysts

Oxidative methane (CH₄) carbonylation promises a direct route to the synthesis of value-added oxygenates such as acetic acid (CH₃COOH). Here, we report a strategy to realize oxidative CH₄ carbonylation through immobilized Ir complexes on an oxide support. Our immobilization approach not only enables direct CH₄ activation but also allows for easy separation and reutilization of the catalyst. Furthermore, we show that a key step, methyl migration, that forms a C-C bond, is sensitive to the electrophilicity of carbonyl, which can be tuned by a gentle reduction to the Ir centers. While the as-prepared catalyst that mainly featured Ir(IV) preferred CH₃COOH production, a reduced catalyst featuring predominantly Ir(III) led to a significant increase of CH₃OH production at the expense of the reduced yield of CH₃COOH.

Molecular design of heterogeneous electrocatalysts using tannic acid-derived metal-phenolic networks

Electrochemistry could play a critical role in the transition to a more sustainable society by enabling the carbon-neutral production and use of various chemicals as well as efficient use of renewable energy resources. A prerequisite for the practical application of various electrochemical energy conversion and storage technologies is the development of efficient and robust electrocatalysts. Recently, molecularly designed heterogeneous catalysts have drawn great attention because they combine the advantages of both heterogeneous solid and homogeneous molecular catalysts. In particular, recently emerged metal-phenolic networks (MPNs) show promise as electrocatalysts for various electrochemical reactions owing to their unique features. They can be easily synthesized under mild conditions, making them eco-friendly, form uniform and conformal thin films on various kinds of substrates, accommodate various metal ions in a single-atom manner, and have excellent charge-transfer ability. In this minireview, we summarize the development of various MPN-based electrocatalysts for diverse electrochemical reactions, such as the hydrogen evolution reaction, the oxygen evolution reaction, the CO₂ reduction reaction, and the N₂ reduction reaction. We believe that this article provides insight into molecularly designable heterogeneous electrocatalysts based on MPNs and guidelines for broadening the applications of MPNs as electrocatalysts.